Gaseous discharge device



Nov; 14, 1939.

GASEOUS DISCHARGE DEVICE c. G. SMITH Original Filed Aug. 25, 1930 =+l l l l ij WM W44 4/ 5 "ZZ I 42 73 X 45 1/3 A? Ad =L IHITIIIIIIIIIA/III 6 Z Y k (EL/J- all) Patented Nov. 14, 1939 UNITED STATES GASEOUS DISCHARGE DEVICE Charles G. Smith, Medford, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Original application August 25, 1930, Serial No. 477,638, now Patent No. 1,962,158, dated June 12, 1934. Divided and this application May 28, 1934, Serial No. 728,000. Renewed January 10,

14 Claims.

My invention relates to gaseous discharge devices. An object of the invention is the provision of such device in which the current flow is capable of being controlled by means of a space charge grid or a magnetic field in a man ner analogous to the control of the electron flow in high vacuum discharge devices.

For many years efforts have been made to provide gas-filled tubes in which a space current discharge produced by ionizing the gas in the tube may be controlled as in high vacuum tubes. In most of the tubes built heretofore for this purpose, no control action comparable to that in high vacuum tubes could be obtained because the positive ions filling the space within the tube would neutralize the control action and render it substantially inefiective.

In accordance with my invention a gaseous discharge device with full control of the current flow by the action of a space charge grid or a magnetic field may be obtained by a very simple arrangement of the electrodes of the device and suitable correlation of the several elements of the discharge path. In the device of my invention I arrange the two electrodes, namely the cathode and anode, between which the discharge that is to be controlled is maintained, in such manner that the cooperating electrode surfaces are separated by a path so short that no substantial ionization is produced by electrons traveling along said path under the influence of the electrostatic field produced by the application of a relatively high potential to the anode.

The cathode is made in the form of a perforated body and on the side of said cathode opposite the anode the gas in the enclosing vessel is maintained in a highly ionized condition, by providing on said side an additional auxiliary electrode, for instance in the form of an incandescent thermionic member and connecting the perforated cathode with the thermionic member in an auxiliary circuit in which the perforated cathode acts as an anode and the thermionic member acts as a cathode, maintaining a gaseous discharge in the space therebetween. The configuration of the perforated cathode and its arrangement with relation to the anode is suchas to substantially prevent positive ions in the space between the auxiliary thermionic cathode and the perforated cathode from entering the space between the perforated cathode and the anode. Electrons, however, enter freely through the openings in the perforated cathode and under the action of the high anode potential maintain a substantially pure electron discharge in the short gap between the perforated cathode and the anode. By providing a control grid extending transversely across the short gap between the perforated cathode and the anode, the electronic discharge can be readily controlled through variation of the potential applied to the control grid, as in high vacuum tubes.

In order that my invention and its features may be fully understood, I shall hereinafter describe it in connection with the accompanying drawing which shows a modification of a gaseous discharge device made in accordance with the invention.

Referring to the drawing, an evacuated cylindrical envelope I of glass or like material has mounted substantially transversely across the same a perforated cathode 2. The cathode comprises a cylindrical sheet-metal member 3 fitting relatively closely the walls of the envelope l and a series of sheet-metal strips extending transversely across the lower end of the sheet-metal member 3 and forming a honeycomb structure having vertically directed channels or perforations 4. The perforated cathode 2 is held in place by means of two supporting wires 1 which are mounted on a press 8 extending'from a reentrant stem 9 on the bottom side of the tube, one of the supporting wires being sealed through the press and forming a terminal conductor l0.

Mounted at a distance below the perforated cathode 2 is a thermionic electrode member ll forming an auxiliary cathode. This auxiliary cathode may be made in the form of a suitably coated filament held on two lead-in wires 12 sealed through the press 8.

The tube has a gas filling either in the form of a quantity of gas, such as helium, or in the form of a vapor, such as mercury vapor or caesium vapor, the presence of the gas filling being indicated by a drop of readily vaporizable metal l5 at the bottom of the tube.

A short distance above the perforated cathode is mounted a main anode I6 which is of cupshaped and has its flat bottom side arranged parallel to the top surface of the perforated cathode 2. The distance between the opposite parallel surfaces is made very small, of the order of the mean free path of the molecules of the gas in the tube and preferably less. The side walls of the cup-shaped anode are shaped so as to lie closely to the upper end of the cylindrical member 3 of the perforated cathode 2, the uper ends of the side walls extending for a substantial distance closely parallel along the walls of the envelope I. Because of this arrangement all long paths between the portions of the perforated cathode 2 and the anode ii are blocked, and direct gaseous conduction between said two electrodes by reason of ionizationby collision along long paths under influence of highvoltages applied to the electrodes is substantially excluded.

Extending transversely across the gap-like space between the upper surface of the perforated cathode 2 and the anode I6 is a grid electrode i8 which serves to control the current fiow between the cathode 2 andthe anode I6. Connection with the anode I6 is effected by means of a lead-in wire I 9 sealed through a press 20 extending from a reentrant stem 21 at the upper end of the tube. The grid electrode i8 is connected to a similar lead-in wire j 22, the portion of the grid lead-in wire extending in the interior of the tube being surrounded by a. glass sleeve 23 so as to exclude direct discharges to the anode portions by reason of the presence of paths of sufilcient length to initiate conduction through ionization by collision.

The cylindrical tube I is surrounded by magnet coils 46 that are suitably energized, as from a source 26, to produce a magnetic field extending longitudinally through the tube in the direction of the discharge path between the auxiliary cathode II and the perforated cathode 2 and the perforations 4 in said cathode. The tube is also provided, in addition to magnet coils 46, with a magnet system having two magnet poles 41 of opposite polarity arranged around the opposite halves of the tube to produce a magnetic field extending transversely across the tube. The magnet system, including the two poles 41, may be excited, for instance, by providing a yoke 48 having mounted thereon an exciting coil 49 that is supplied with excitation current by means of a pair of leads 50. Under the action of the transverse magnetic field between the poles 41, the electrons flowing upwardly towards the cathode 2 will be turned sideways towards the walls of the vessel I. By making the current through the exciting coil 49 sufliciently large, the transverse field can be given a strength at which substantially all electrons flowing upwardly in the space below the cathode 2 will be turned away towards the sides before reaching the perforated cathode, thereby cutting off or varying the electron supply for the main discharge path between the cathode 2 and the anode it. By varying the current through the coil 49, the strength of this transverse field may be correspondingly varied and the flow of electrons towards the perforated cathode and the space above it controlled at will, thus securing modulation of the current flow in the main discharge path independently of the control action exercised by the grid IS on said path. By the use of such combined modulation and grid control arrangements, the oscillations produced in an oscillating circuit may be modulated in accordance with the impulses impressed on the coil 49 of the transverse magnet system. Other applications and modifications of this arrangement will suggest themselves to those skilled in the art.

The tube may be connected to operate as an oscillator by being connected in some suitable oscillating circuit, as for example that shown in the drawing. The auxiliary thermionic cathode l i is connected to a heating source, for instance in the form of a battery 3|. A source of excitation current, such as a battery 32, has its negative terminal connected to the auxiliary cathode Ii and its positive terminal to the perforated cathode 2 which acts as an anode with respect to the auxiliary cathode ll so as to maintain between said electrodes a gaseous discharge that ionizes nected an output circuit 33, including a tuned oscillating circuit 4| comprising a condenser 42 and an inductance 43, and a serially connected source of plate potential, such as a battery 35, applying a relatively high positive potential to the plate.

A pair of coupling coils 44 couple the output circuit 33 with the input circuit 36, feeding back energy from the output circuit into the input circuit to maintain sustained oscillations in the tuned circuit 4|, as in high vacuum tube oscillators. The biasing battery 38 is so arranged as to permit application of a negative biasing potential to the grid. The produced high frequency oscillations may be suitably utilized as by means of a circuit, including a coil 45 coupled with the oscillating coil 43 in the tuned circuit 4|.

Under the action of the excitation source 32, an ionized gas discharge is maintained between the auxiliary cathode II and the perforated cathode 2. Electrons are produced in abundance in this space by the cumulative ionization by collision of the electrons flowing toward the anode. The space below the perforated cathode is thus filled with electrons and positive ions. The electrons flow upwardly towards the perforated cathode 2 and, partially because of the acquired velocity, they will pass through the perforations 4 and enter into the space 6 between the perforated cathode and the anode I6. The entering electrons come in this space under the influence of the strong field produced by the high positive potential on the anode, and a current flow between the perforated cathode 2 and the anode i6 is thus produced, as in a high vacuum tube.

By reason of the relatively long and close 'perforations 4 in the perforated cathode 2 very few of the positive ions from the space below get into the main discharge path between the cathode and the anode, so that the main discharge space contains only few positive ions and the discharge is substantially purely electronic.

This substantially pure electron current is readily controlled by varying the potential of the grid l8, there being insufiicient positive ions in the space 6 to neutralize the charge on the control grid and render it ineffective as in prior art constructions.

A limited amount of positive ions is present in the main discharge space 6, either having passed through the perforations in the cathode 2 or having been produced by an isolated collision of an electron with a molecule. Such positive ions are only few in number and insufiicient to neutralize or detrimentally affect the control action of the grid l8, the limited number of positive ions in the space l6 being beneficial in that they neutralize the space charge and reduce the impedance of the main discharge path.

The biasing battery 38 in the input circuit connected to the grid I8 is so arranged as to apply a sufiiciently negative biasing potential to the grid so as to reduce the electron current tending to collect on the grid.

Tubes of the foregoing construction will operate with very effective control of the current in the main discharge path by the grid action, with by the application of very relatively large currents in the main discharge path and up to relatively high voltages in the out- .put circuit. It is accordingly possible to control very large amounts of power in the output circuit little input energy in the input circuit. V

For the operativeness of the device it is absolutely essential that the several elements of the tube be so arranged with respect to each other as to prevent the formation of an ionized gas discharge in the main discharge path between the perforated cathode 2 and the anode Hi. This is secured by the special construction which blocks the entrance of excessively large numbers of positive ions into the short gap main discharge path, and the blocking of all long paths between the anode l6 and the perforated cathode 2 as well as the grid it.

The honeycomb construction of the perforated cathode is particularly effective in preventing entrance of the positive ions from the space below the cathode into the main discharge space while at the same time permitting relatively free flow of electrons through the perforations, especially in combination with the action of the longitudinal magnetic field produced by the coil it. The magnetic field keeps the eletcrons flowing upwardly in straight vertical direction, and facilitates their passing through the perforations without going to the walls forming the honeycomb structure and overcoming the attraction exercised by the positively charged walls on the negative electron charges.

By reason of the relatively great length of these perforations t, the likelihood of positive ions passing through the honeycomb structure is very small, inasmuch as the positive charge of the walls of the perforations exercises a cumulative repelling action over a substantial length of the path of flow of such positive ions, which have only relatively small velocity, thereby assuring a strong blocking action against their entrance into the main discharge path.

The combined effects of the honeycomb structure and the magnetic field thus enable the use of relatively wide perforations in the main cathode i, and secure an abundant supply of electrons for maintaining the main discharge under control of the grid it. The honeycomb cathode structure thus acts like a wide-mesh grid for electrons, but like a close-mesh grid for positive ions.

The longitudinal magnetic field gives also other effects beneficial for the operation of the tube. Without the field many of the electrons in the discharge space below the perforated cathode 2 collide with the surrounding glass walls and get trapped there, attracting positive ions from the discharge, thus reducing the ionization and conductivity of the space. With the longitudinal field present, electrons either fiow straight along the magnetic lines of force without reaching the glass walls, or move along small helices without reaching the Wall. In the latter case the paths of the electrons are lengthened, giving additional,ionization, while at the same time reducing the loss of ionization by preventing the trapping of electrons on the glass walls.

Because of the foregoing effect of the longitudinal magnetic field in preserving the ionization in the discharge path between the auxiliary cathode ill and the perforated cathode 2, it is possible to maintain in the space between said electrodes an ionized gas discharge at low pressures which would otherwise be insufficient to secure such discharge. This enables the construction of tubes with relatively low pressures and yet maintaining'the main discharge with electrons supplied from an ionized gas body, the low pressure permitting farther spacing of the electrodes in the controlled discharge path and securing effective control action for higher voltages than would otherwise be possible.

The various details of construction and arrangements referred to above in describing the various modifications of my invention are intended for illustrative purposes only, and I desire it to be distinctly understood that my invention is not limited thereto as many modifications thereof will suggest themselves to those skilled in the art. I accordingly desire that the appended claims be given a broad construction in accordance with the scope of the invention.

This application is a division of my Patent, No. 1,962,158, dated June 12, 1934.

What is claimed is:

1. A gaseous conduction device comprising an envelope containing a cathode, an electrode adapted to operate as an anode therefor and spaced therefrom, a gas filling at a pressure sufficiently high to produce copious ionization upon the passage of a' discharge therein, an auxiliary eelctrode interposed between said cathode and anode and spaced from said anode an insulatingly short distance, said auxiliary electrode having a passage therethrough to permit electrons to pass therethrough to said anode, and means for creating a magnetic field in the discharge path between said cathode and anode and transverse thereto to cotnrol the amount of current flowing to said anode.

2. A gaseous conduction device comprising an envelope containing a cathode, an electrode adapted to operate as an anode therefor and spaced therefrom, a gas filling at a pressure sufficiently high to produce copious ionization upon the passage of a discharge therein, an auxiliary eelctrode interposed between said cathode and anode and spaced from said anode an insulatingly short distance, said auxiliary electrode having a passage therethrough to permit electrons to pass therethrough to said anode, a control electrode interposed between said auxiliary electrode and anode for regulating the space discharge between said auxiliary electrode and anode, and means for creating a magnetic field in the discharge path between said cathode and anode and transverse thereto to control the amount of current flow to said anode.

3. A gaseous conduction device comprising an envelope containing a cathode, an electrode adapted to operate as an anode therefor and spaced therefrom, a gas filling at a pressure sufficiently high to produce copious ionization upon the passage of a discharge therein, an auxiliary conducting member disposed adjacent the discharge path between said cathode and anode and spaced from said anode an insulatingly short distance, and means for creating a magnetic field in the discharge path between said cathode and anode and transverse thereto to control the amount of current flow to said anode.

4. A gaseous conduction device comprising a gas-tight vessel containing a gas at a pressure sufficient to secure its ionization and maintenance of a gaseous discharge therein, a cathode having perforations over its surface, an anode disposed adjacent one side of said cathode and spaced therefrom by a gap sufficiently short to prevent a gaseous discharge due to gas ionization between the opposed electrode surfaces under application of a high voltage therebetween, an additional electrode outside of said gap to be operated as a cathode with respect to said perforated cathode and maintain therewith a gaseous discharge for ionizing the gas therebetween and generating electrons tending to enter through the cathode perforations the gap between the perforated cathode and anode, a control grid between said cathode and said anode to control the discharge therebetween, and means for controlling the current flow between said additional electrode and perforated cathode.

5. A gaseous conduction device comprising a gas-tight vessel containing a gas at a pressure sufiicient to secure its ionization and maintenance of a gaseous discharge therein, a, cathode having perforations over its surface, an anode disposed adjacent one side of said cathode and spaced therefrom by a gap sufficiently short to prevent a gaseous discharge due to gas ionization between the opposed electrode surfaces under application of a high voltage therebetween, an additional electrode outside of said gap to be operated as a cathode with respect to said perforated cathode and maintain therewith a gaseous discharge for ionizing the gas therebetween and generating electrons tending to enter through the cathode perforations the gap between the perforated cathode and anode, a control grid between said perforated cathode and said anode to control the discharge therebetween, an oscillating circuit connected to said electrodes whereby oscillations may be produced by said device, and means for controlling the current fiow between said cathode and perforated cathode to modulate the oscillations produced.

6. A gaseous conduction device comprising a gas-tight vessel containing a gas at a pressure sufficient to secure its ionization and maintenance of a gaseous discharge therein, a cathode having perforations over its surface, an anode disposed adjacent one side of said cathode and spaced therefrom by a gap sufficiently short to prevent a gaseous discharge due to gas ionization between the opposed electrodesurfaces under application of a high voltage therebetween, an additional electrode outside of said gap to be operated as a cathode with respect to said perforated cathode and maintain therewith a gaseous discharge for ionizing the gas therebetween and generating electrons tending to enter through the cathode perforations the gap between the perforated cathode and anode. a control grid between said cathode and said anode to control the discharge therebetween, means for creating a magnetic field in the discharge path between said cathode and anode and transverse thereto, an oscillating circuit connected to said electrodes, whereby oscillations may be produced by said device, and means for varying said magnetic field to modulate the oscillations produced.

'7. An electrical gaseous conduction device comprising a receptacle containing a gas 'at a pressure sufficient to produce copious ionization upon the passage of a discharge therein, an electrode having perforations over its surface, an anode disposed adjacent one side of said perforated electrode and spaced therefrom by a gap sufliciently short to prevent a gaseous discharge due to gas ionization between the opposed electrode surfaces under application of a high voltage therebetween, electrode means for maintaining a gaseous discharge in the space at the other side of said perforated electrode from said anode for ionizing the gas therein and generating, electrons tending to enter through the electrode perforations the gap between said perforated electrode and said anode, 'a control grid between said perforated electrode and said anode to control the discharge therebetween, and means for controlling the current flow in said gaseous ionizing discharge.

8. A gaseous conduction device comprising an envelope containing a cathode, an electrode adapted to operate as an anode therefor and spaced therefrom, a gas filling at a pressure sufficiently high to produce copious ionization upon the passage of a discharge therein, an auxiliary electrode interposed between said cathode and anode, and spaced from said anode an insulatingly short distance, said auxiliary electrode having a passage therethrough to permit electrons to pass therethrough to said anode, said passage being of relatively extended length and surrounded by a relatively extended wall surface of said auxiliary electrode, and means for creating a magnetic field in the discharge path between said cathode and anode and transverse thereto, a portion of said field being disposed adjacent said auxiliary conducting member.

9. A gaseous conduction device comprising an envelope containing a cathode, an electrode adapted to operate as an anode therefor and spaced therefrom, a, gas filling at a pressure sufficiently high to produce copious ionization upon the passage of a discharge therein, an auxiliary electrode interposed between said cathode and anode and spaced from said anode an insulatingly short distance, said auxiliary electrode having a passage therethrough to permit electrons to pass therethrough to said anode, means for creating a magnetic field transverse to the discharge path between said cathode and anode, and means for creating a magnetic field longitudinal to said discharge path and substantially in line with said passage.

10. A gaseous conduction device comprising an envelope containing a cathode, an electrode adapted to operate as an anode therefor and spaced therefrom, a gas filling at a pressure sufficiently high to produce copious ionization upon the passage of a discharge therein, an auxiliary electrode interposed between said cathode and anode and spaced from said anode an insulatingly short distance, said auxiliary electrode having a passage therethrough to permit electrons to pass therethrough to said anode, a control electrode interposed between said auxiliary electrode and anode for regulating the space discharge between said auxiliary electrode and anode, means for creating a magnetic field transverse to the discharge path between said cathode and anode, and means for creating a magnetic field longitudinal to said discharge path and substantially in line with said passage.

11. A gaseous conduction device comprising an envelope containing a' cathode, an electrode adapted to operate as an anode therefor and spaced therefrom, a gas filling at a pressure sufficiently high to produce copious ionization upon the passage of a discharge therein, an auxiliary electrode interposed between said cathode and anode and spaced from said anode an insulatingly short distance, said auxiliary electrode having a passage therethrough to permit electrons to pass therethrough to said anode, and means for creating a variable magnetic field in the discharge path between said cathode and anode to vary the amount of current flow to said anode.

12. A gaseous conduction device comprising an envelope containing a cathode, an electrode the passage of a discharge therein, an auxiliary eelctrode interposed between said cathode and anode and spaced from .said anode an insulatingly short distance, said auxiliary electrode having a passage therethrough to permit electrons to pass therethrough to said anode,'a control electrode interposed between said auxiliary electrode and anode for regulating the space discharge between said auxiliary electrode and anode, and means for creating a variable magnetic field in the discharge path between said cathode and anode to vary the amount of current flow to said anode.

13. A gaseous conduction device comprising an envelope containing a cathode, an electrode adapted to operate as an anode therefor and spaced therefrom, a gas filling at a pressure sufliciently high to produce copious ionization upon the passage of a discharge therein, an auxiliary conducting member disposed adjacent the discharge path between said cathode and anode and spaced from said anode an insulatingly short distance, and means for creating a variable magnetic field in the discharge path between said cathode and anode to vary the amount of c rent flow to said anode. A

14. A gaseous conduction device comprising a gas-tight vessel containing a gas at a pressure sufiicient to secure its ionization and maintenance of a gaseous discharge therein, a cathode having perforations over its surface, anv anode disposed adjacent one side of said cathode and spaced therefrom by a gap sufliciently short to prevent a gaseous discharge due to gas ionization between the opposed electrode surfaces under application of a high voltage therebetween, an additional electrode outside of said gap to be operated as a cathode with respect to said perforated cathode and maintain therewith a gaseous discharge for ionizing the gas therebetween and generating electrons tending to enter through the cathode perforations the gap between the perforated cathode and anode', a control grid between said cathode and said anode to control the discharge therebetween, means for creating a magnetic field in the discharge path between said cathode and anode, an oscillating circuit connected to said electrodes, whereby oscillations may be produced by said device, and means for varying said magnetic field to modulate the oscillations produced.

CHARLES G.' SMITH. 

